Winter brings a somber note to the garden, after which we look to spring to lighten up the vista, notes clematis expert John Howells. The plant that does this best, he says, is Clematis montana. Huge sweeps of fragrant color, involving thousands of small flowers, climb into trees, cover walls and embellish shrubs, and while no one montana flowers for long, a sequence of montanas can flower from April to September, some producing attractive seed heads. Howells's guide to this vigorous, easy-to-grow species and its varieties is illustrated with 225 color plates.